/* ==========================================================================
   HỆ THỐNG QUIZ PHƯỜNG TÙNG THIỆN - BASE DESIGN SYSTEM
   Phong cách: Trang trọng, Hiện đại, Tin cậy, Chuẩn nhận diện hành chính
   ========================================================================== */

@import url('https://fonts.googleapis.com/css2?family=Inter:wght@400;500;600;700;800&display=swap');

:root {
  /* Color Palette */
  --primary: #b91c1c;         /* Đỏ cờ trang trọng */
  --primary-hover: #991b1b;
  --primary-active: #7f1d1d;
  --primary-light: #fef2f2;
  --primary-border: #fecaca;

  --accent: #d97706;          /* Vàng ánh kim / Vàng sao */
  --accent-hover: #b45309;
  --accent-light: #fffbeb;
  --accent-border: #fde68a;

  --success: #16a34a;
  --success-light: #f0fdf4;
  --warning: #eab308;
  --warning-light: #fefce8;
  --danger: #dc2626;
  --danger-light: #fef2f2;
  --info: #2563eb;
  --info-light: #eff6ff;

  --text-main: #0f172a;       /* Slate 900 */
  --text-muted: #475569;      /* Slate 600 */
  --text-subtle: #64748b;     /* Slate 500 */
  --text-inverse: #ffffff;

  --bg-body: #f8fafc;         /* Slate 50 */
  --bg-card: #ffffff;
  --bg-subtle: #f1f5f9;       /* Slate 100 */
  --border-color: #e2e8f0;    /* Slate 200 */
  --border-focus: #b91c1c;

  /* Typography */
  --font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Helvetica, Arial, sans-serif;
  --font-xs: 0.75rem;     /* 12px */
  --font-sm: 0.875rem;    /* 14px */
  --font-base: 1rem;       /* 16px */
  --font-lg: 1.125rem;    /* 18px */
  --font-xl: 1.25rem;     /* 20px */
  --font-2xl: 1.5rem;     /* 24px */
  --font-3xl: 1.875rem;   /* 30px */
  --font-4xl: 2.25rem;    /* 36px */

  /* Spacing */
  --space-1: 0.25rem;  /* 4px */
  --space-2: 0.5rem;   /* 8px */
  --space-3: 0.75rem;  /* 12px */
  --space-4: 1rem;     /* 16px */
  --space-5: 1.25rem;  /* 20px */
  --space-6: 1.5rem;   /* 24px */
  --space-8: 2rem;     /* 32px */
  --space-10: 2.5rem;  /* 40px */
  --space-12: 3rem;    /* 48px */

  /* Radius */
  --radius-sm: 6px;
  --radius-md: 10px;
  --radius-lg: 16px;
  --radius-xl: 24px;
  --radius-full: 9999px;

  /* Shadows */
  --shadow-sm: 0 1px 2px 0 rgba(15, 23, 42, 0.05);
  --shadow-md: 0 4px 6px -1px rgba(15, 23, 42, 0.08), 0 2px 4px -2px rgba(15, 23, 42, 0.05);
  --shadow-lg: 0 10px 15px -3px rgba(15, 23, 42, 0.08), 0 4px 6px -4px rgba(15, 23, 42, 0.04);
  --shadow-xl: 0 20px 25px -5px rgba(15, 23, 42, 0.1), 0 8px 10px -6px rgba(15, 23, 42, 0.05);

  /* Layout */
  --container-max-w: 1120px;
  --form-max-w: 540px;
  --transition-fast: 0.15s ease;
  --transition-normal: 0.25s ease;
}

/* CSS Reset & Base */
*, *::before, *::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html {
  font-size: 16px;
  -webkit-text-size-adjust: 100%;
  scroll-behavior: smooth;
}

body {
  font-family: var(--font-family);
  font-size: var(--font-base);
  line-height: 1.6;
  color: var(--text-main);
  background-color: var(--bg-body);
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  overflow-x: hidden;
}

/* Layout Utilities */
.container {
  width: 100%;
  max-width: var(--container-max-w);
  margin-left: auto;
  margin-right: auto;
  padding-left: var(--space-4);
  padding-right: var(--space-4);
}

.main-content {
  flex: 1;
  padding-top: var(--space-6);
  padding-bottom: var(--space-10);
}

/* Header & Banner */
.site-header {
  background: linear-gradient(135deg, #991b1b 0%, #b91c1c 50%, #7f1d1d 100%);
  color: var(--text-inverse);
  box-shadow: var(--shadow-md);
  position: relative;
  overflow: hidden;
}

.site-header::after {
  content: '';
  position: absolute;
  bottom: 0;
  left: 0;
  right: 0;
  height: 4px;
  background: linear-gradient(90deg, #f59e0b, #fbbf24, #d97706);
}

.header-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: var(--space-4) 0;
}

.brand-wrapper {
  display: flex;
  align-items: center;
  gap: var(--space-3);
  text-decoration: none;
  color: inherit;
}

.brand-logo-badge {
  width: 44px;
  height: 44px;
  background-color: #fff;
  border-radius: var(--radius-full);
  display: flex;
  align-items: center;
  justify-content: center;
  box-shadow: var(--shadow-sm);
  font-size: var(--font-xl);
  font-weight: 800;
  color: var(--primary);
  flex-shrink: 0;
}

.brand-text h1 {
  font-size: var(--font-lg);
  font-weight: 700;
  line-height: 1.25;
  letter-spacing: -0.01em;
}

.brand-text p {
  font-size: var(--font-xs);
  color: #fecaca;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  font-weight: 600;
}

.header-nav {
  display: flex;
  gap: var(--space-3);
}

.nav-link {
  color: #fee2e2;
  text-decoration: none;
  font-size: var(--font-sm);
  font-weight: 500;
  padding: var(--space-2) var(--space-3);
  border-radius: var(--radius-sm);
  transition: background var(--transition-fast), color var(--transition-fast);
}

.nav-link:hover {
  background: rgba(255, 255, 255, 0.15);
  color: #fff;
}

/* Card Component */
.card {
  background-color: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  padding: var(--space-6);
  box-shadow: var(--shadow-sm);
  transition: box-shadow var(--transition-normal);
}

.card:hover {
  box-shadow: var(--shadow-md);
}

.card-header {
  margin-bottom: var(--space-5);
  padding-bottom: var(--space-4);
  border-bottom: 1px solid var(--border-color);
}

.card-title {
  font-size: var(--font-xl);
  font-weight: 700;
  color: var(--text-main);
}

.card-subtitle {
  font-size: var(--font-sm);
  color: var(--text-muted);
  margin-top: var(--space-1);
}

/* Form Elements */
.form-group {
  margin-bottom: var(--space-5);
}

.form-label {
  display: block;
  font-size: var(--font-sm);
  font-weight: 600;
  color: var(--text-main);
  margin-bottom: var(--space-2);
}

.form-label .required {
  color: var(--danger);
  margin-left: var(--space-1);
}

.form-input,
.form-select {
  width: 100%;
  font-family: inherit;
  font-size: 1rem; /* >= 16px chống tự động zoom trên iOS Safari */
  min-height: 46px; /* Touch target chuẩn */
  padding: 0.75rem 1rem;
  border: 1.5px solid var(--border-color);
  border-radius: var(--radius-md);
  background-color: #fff;
  color: var(--text-main);
  transition: border-color var(--transition-fast), box-shadow var(--transition-fast);
}

.form-input:focus,
.form-select:focus {
  outline: none;
  border-color: var(--border-focus);
  box-shadow: 0 0 0 3px rgba(185, 28, 28, 0.15);
}

.form-input.is-invalid,
.form-select.is-invalid {
  border-color: var(--danger);
  background-color: #fffaf0;
}

.form-input.is-invalid:focus,
.form-select.is-invalid:focus {
  box-shadow: 0 0 0 3px rgba(220, 38, 38, 0.15);
}

.form-input::placeholder {
  color: var(--text-subtle);
}

.field-error {
  font-size: var(--font-xs);
  font-weight: 600;
  color: var(--danger);
  margin-top: 0.35rem;
  display: flex;
  align-items: center;
  gap: 0.25rem;
}

.form-hint {
  font-size: var(--font-xs);
  color: var(--text-muted);
  margin-top: var(--space-1);
}

/* Modal Dialog */
.modal-overlay {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background-color: rgba(15, 23, 42, 0.65);
  backdrop-filter: blur(4px);
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 9999;
  padding: var(--space-4);
  opacity: 0;
  visibility: hidden;
  transition: opacity var(--transition-normal), visibility var(--transition-normal);
}

.modal-overlay.active {
  opacity: 1;
  visibility: visible;
}

.modal-content {
  background: var(--bg-card);
  border-radius: var(--radius-lg);
  box-shadow: var(--shadow-xl);
  max-width: 500px;
  width: 100%;
  overflow: hidden;
  transform: scale(0.95);
  transition: transform var(--transition-normal);
  border: 1px solid var(--border-color);
}

.modal-overlay.active .modal-content {
  transform: scale(1);
}

.modal-header {
  padding: var(--space-5) var(--space-6);
  border-bottom: 1px solid var(--border-color);
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.modal-title {
  font-size: var(--font-lg);
  font-weight: 700;
  color: var(--text-main);
}

.modal-body {
  padding: var(--space-6);
  color: var(--text-main);
  line-height: 1.5;
}

.modal-footer {
  padding: var(--space-4) var(--space-6);
  background-color: var(--bg-subtle);
  border-top: 1px solid var(--border-color);
  display: flex;
  justify-content: flex-end;
  gap: var(--space-3);
}

/* Loading button state */
.btn.loading {
  position: relative;
  pointer-events: none;
  opacity: 0.8;
  color: transparent !important;
}

.btn.loading::after {
  content: '';
  position: absolute;
  width: 20px;
  height: 20px;
  border: 2.5px solid rgba(255, 255, 255, 0.3);
  border-radius: 50%;
  border-top-color: #fff;
  animation: spin 0.8s linear infinite;
}

.btn-secondary.loading::after {
  border-color: rgba(15, 23, 42, 0.2);
  border-top-color: var(--text-main);
}

@keyframes spin {
  to { transform: rotate(360deg); }
}

/* Buttons */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-2);
  font-family: inherit;
  font-size: var(--font-base);
  font-weight: 600;
  padding: 0.75rem 1.5rem;
  border-radius: var(--radius-md);
  border: 1px solid transparent;
  cursor: pointer;
  text-decoration: none;
  transition: all var(--transition-fast);
  white-space: nowrap;
}

.btn:disabled {
  opacity: 0.6;
  cursor: not-allowed;
  pointer-events: none;
}

.btn-primary {
  background-color: var(--primary);
  color: var(--text-inverse);
  box-shadow: 0 2px 4px rgba(185, 28, 28, 0.25);
}

.btn-primary:hover {
  background-color: var(--primary-hover);
  box-shadow: 0 4px 8px rgba(185, 28, 28, 0.35);
}

.btn-secondary {
  background-color: var(--bg-card);
  border-color: var(--border-color);
  color: var(--text-main);
}

.btn-secondary:hover {
  background-color: var(--bg-subtle);
  border-color: #cbd5e1;
}

.btn-accent {
  background-color: var(--accent);
  color: #fff;
}

.btn-accent:hover {
  background-color: var(--accent-hover);
}

.btn-block {
  width: 100%;
}

.btn-lg {
  padding: 0.875rem 1.75rem;
  font-size: var(--font-lg);
}

/* Badges & Status */
.badge {
  display: inline-flex;
  align-items: center;
  padding: 0.25rem 0.625rem;
  border-radius: var(--radius-full);
  font-size: var(--font-xs);
  font-weight: 700;
  line-height: 1;
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

.badge-primary {
  background-color: var(--primary-light);
  color: var(--primary);
  border: 1px solid var(--primary-border);
}

.badge-success {
  background-color: var(--success-light);
  color: var(--success);
  border: 1px solid #bbf7d0;
}

.badge-warning {
  background-color: var(--warning-light);
  color: var(--accent-hover);
  border: 1px solid #fef08a;
}

.badge-info {
  background-color: var(--info-light);
  color: var(--info);
  border: 1px solid #bfdbfe;
}

/* Alerts */
.alert {
  padding: var(--space-4);
  border-radius: var(--radius-md);
  margin-bottom: var(--space-5);
  font-size: var(--font-sm);
  border: 1px solid transparent;
}

.alert-info {
  background-color: var(--info-light);
  color: #1e40af;
  border-color: #bfdbfe;
}

.alert-warning {
  background-color: var(--warning-light);
  color: #854d0e;
  border-color: #fde047;
}

.alert-danger {
  background-color: var(--danger-light);
  color: #991b1b;
  border-color: #fecaca;
}

/* Footer */
.site-footer {
  margin-top: auto;
  background-color: #fff;
  border-top: 1px solid var(--border-color);
  padding: var(--space-6) 0;
  text-align: center;
  font-size: var(--font-sm);
  color: var(--text-muted);
}

/* Responsive adjustments */
@media (max-width: 640px) {
  :root {
    --space-6: 1.25rem;
    --space-8: 1.5rem;
  }

  .header-inner {
    flex-direction: column;
    align-items: flex-start;
    gap: var(--space-3);
  }

  .brand-text h1 {
    font-size: var(--font-base);
  }

  .header-nav {
    width: 100%;
    justify-content: flex-start;
    overflow-x: auto;
    padding-bottom: var(--space-1);
  }

  .card {
    padding: var(--space-4);
    border-radius: var(--radius-md);
  }
}